ranlib bleating about dirmod.o being empty

I'm getting rather tired of reading these warning messages in OS X builds:

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file:
libpgport.a(dirmod.o)has no symbols
 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file:
libpgport_srv.a(dirmod_srv.o)has no symbols
 

The reason for this warning is that dirmod.o contains no functions that
aren't Windows-specific.  As such, it seems like putting it into the
list of "always compiled" port modules is really a mistake.  Any
objections to switching it to be built only on Windows?
        regards, tom lane